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Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

GLACIERS OF UNAKWIK INLET AND COLLEGE FIORD         313
filling depressions back of morainal dams." The larger of these, Lake Coghill, may be held in by recessional terminal moraines of either Dartmouth or Williams Glacier.
Of the lateral moraines the one on the western side of College Point, between Harvard and Yale arms, is typical (PI. CXXVI), consisting of till and stratified gravels, evidently built between the glacier and the mountain side. It has several terrace levels forming a morainic prow on both sides of College Point. In some places the terrace is surmounted by push moraines, in other places with ridges which may either be constructional or due to stream channeling. Most of these ridges are unquestionable push moraines, showing that the ice margin oscillated at this edge. The lowest terrace slopes southwestward from the 900 foot contour above the end of Yale Glacier to an elevation of 575 feet near the end of College Point. Gravel remnants suggesting a corresponding moraine on the eastern side of Yale Arm descend from an elevation of 1017 feet near the glacier to 200 feet about three miles to the southwest. These gravel remnants are covered by distinctive vegetation.
Above timber line, but in the zone of alder growth, on the slopes of Mt. Emerson, south of Holyoke Glacier certain shelves or benches (Fig. 43) suggest moraine terraces. In places there are three levels, with alluvial fans and snowbanks above. Between Barnard and Holyoke glaciers there is one shelf, not seen north of Barnard Glacier. Near Holyoke Glacier it is about 1500 feet above sea level. Below Mt. Emerson it slopes southward down to approximately 1200 feet, dying out opposite Coghill River, and a bench above this one extends a little farther south.
The outwash gravels near Amherst, Crescent, Williams, and Dartmouth Glaciers form the largest area of this kind of deposit in College Fiord.
Below sea level there are no definitely proved submerged moraines except the two moraine bars at the entrance to Port Wells, described in the next chapter. The 342 foot ridge or swell between Smith and Bryn Mawr Glaciers, rising 400 feet above the fiord bottom to the north, may be a submerged moraine. The 174 foot swell just west of lower Coghill River may possibly be a submerged moraine. As already indicated the shallow southern part of College Fiord seems more likely to be due to lack of excavation than to glacial deposition under water. A minor, projecting point on the western side of the fiord, near the 264 foot sounding, in this southern portion, suggests a submerged moraine bar, but the soundings are not detailed enough to determine this.
Vegetation in College Fiord. The vegetation in College Fiord furnishes important evidence concerning the episodes of former glaciation. Gilbert pointed out in 1899 some of the relationships of trees near the Yale, the Harvard, and the cascading glaciers, and stated that "a little farther, south the coast is forested, and the trees climb up a few hundred feet on the moraine heaps under the hanging glaciers. They are separated from the ice, first by a broad belt of alders, and then by a barren zone. As the spruce forest in College Fiord nowhere stands close to the ice, but is separated by a barren zone, it seems fair to assume that the ice has occupied this zone so recently that the period since its shrinkage has not sufficed for reforesting; but no facts are recorded tending to show the nature of the changes immediately preceding our visit." As we have already shown, by July, 1910, most of the barren zones had been overridden.
We observed the following additional relationships of vegetation to the fiord walls